linux-kernel - Re: [PATCH v3 1/1] regmap: Synchronize cache for the page selector

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Message-ID: <Z4-hMdUUTeQHN5W_@smile.fi.intel.com>
Date: Tue, 21 Jan 2025 15:29:21 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Marek Szyprowski <m.szyprowski@...sung.com>
Cc: Mark Brown <broonie@...nel.org>, linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Danilo Krummrich <dakr@...nel.org>,
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
	DRI mailing list <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH v3 1/1] regmap: Synchronize cache for the page selector

On Tue, Jan 21, 2025 at 08:33:09AM +0100, Marek Szyprowski wrote:
> On 17.01.2025 18:28, Andy Shevchenko wrote:
> > On Fri, Jan 17, 2025 at 05:05:42PM +0100, Marek Szyprowski wrote:

> > Does it fail in the same way?
> 
> Yes, the hw revision is reported as zero in this case: LT9611 revision: 
> 0x00.00.00

Hmm... This is very interesting! It means that the page selector is a bit
magical there. Dmitry, can you chime in and perhaps shed some light on this?

> >> Does it mean that there is really a bug in the driver?
> > Without looking at the datasheet it's hard to say. At least what I found so far
> > is one page of the I²C traffic dump on Windows as an example how to use their
> > evaluation board and software, but it doesn't unveil the bigger picture. At
> > least what I think is going on here is that the programming is not so easy as
> > just paging. Something is more complicated there.
> >
> > But at least (and as Mark said) the most of the regmap based drivers got
> > the ranges wrong (so, at least there is one bug in the driver).
> 
> I can do more experiments if this helps. Do you need a dump of all 
> regmap accesses or i2c traffic from this driver?

It would be helpful! Traces from the failed and non-failed cases
till the firmware revision and chip ID reading would be enough to
start with.

-- 
With Best Regards,
Andy Shevchenko